EUGENE, Ore. — Jordan Williamson hit a 37-yard field goal in overtime and No. 14 Stanford upset top-ranked Oregon, 17-14, Saturday night, denying the Ducks a chance to clinch the Pac-12 North and derailing their straight shot at the BCS championship game.

If both Stanford and Oregon win their final games next weekend, both will finish with one conference loss, which means Stanford will win the head-to-head matchup and go to the Pac-12 championship game for a chance to play in the Rose Bowl.

Stanford (9-2, 7-1) will visit No. 17 UCLA, which defeated No. 21 Southern Cal, 32-29, earlier in the day to claim the Pac-12 South. Oregon (10-1, 7-1) will play rival Oregon State in the annual Civil War rivalry game in Corvallis.

The loss snapped a 13-game winning streak for the Ducks, which was longest current streak in the nation. It was Stanford’s fifth straight win.

Oregon wasn’t the only upset at the top of the rankings: No. 2 Kansas State got routed by Baylor, leaving unbeaten and No. 3 Notre Dame as the likely top team when the BCS standings are released Sunday night. The losses by Oregon and Kansas State also open the door for defending champion and once-beaten Alabama to get back in the hunt to play in the BCS championship game.

Oregon was the only Pac-12 team that Stanford hadn’t defeated over the past two seasons. But the Cardinal’s tough defense smothered the highest-scoring team in the nation.

Alejandro Maldanado missed a 41-yard field goal for the Ducks to open overtime, bouncing the kick off the left upright.

Trailing, 14-7, Stanford went for it on fourth and 1 on the Oregon 12 with 2:17 left in regulation and Ryan Hewitt ran for the first down.

Hogan hit Zach Ertz with a 10-yard scoring pass to tie it at 14 with 1:35 to go. Ertz fought to gain control of the ball with a defender as he fell to the turf on top of a Ducks player. The play was initially ruled incomplete, but a video review overturned it for the game-tying touchdown.

Despite a pass interference call that gave them a crucial first down, the Ducks were forced to punt on the ensuing series and Stanford took over with 36 seconds to go, and the game went to overtime.

Stanford held Ducks running back Kenjon Barner, who was averaging 136 yards rushing a game, to just 66 yards. Overall, the Ducks managed only 198 yards on the ground.

Oregon’s top rusher was quarterback Marcus Mariota, who ran for 89 yards.

Stanford stopped what appeared to be a sure first-quarter Oregon TD drive when Mariota took off on a 77-yard keeper to the Stanford 15. But the Ducks couldn’t get much closer, and Stanford got the stop when Oregon went for it on fourth and 2 on the 7.

Stanford scored first on Hogan’s 1-yard plow into the end zone in the second quarter.

Oregon tried again on fourth and 4 midway through the quarter, but was unsuccessful, this time when Mariota’s pass to tight end Colt Lyerla fell incomplete.

When Oregon took over on downs from Stanford on the next series, the Ducks marched 59 yards in three plays — capped by Mariota’s 28-yard touchdown pass to Keanon Lowe — to tie it at 7-all.

Oregon extended its lead to 14-7 on DeAnthony Thomas’s 6-yard run in the third quarter, but missed a chance when Maldonado’s 42-yard field goal attempt went wide right.